The present invention relates generally to optical modulators, and more particularly to a device for modulating light transmission through a metallic film.
The invention described herein comprises an improvement on a previously described device, wherein the intensity of a directed light beam may be modulated by transmission through or reflection off a metallic film. A theoretical discussion of the principles forming a foundation of the invention and of experimental work related thereto may be found in "Hight Transparency of Classically Opaque Metallic Films", by R. Dragila et al. Phys Rev Lett 55:10, 1117-20 (2 Sep 85), hereinafter called "the reference", the same being incorporated herein by reference. The structure described in the reference consists of a metal layer sandwiched between layers of a dielectric. Transmission of light through the metal layer obtains if proper selection of materials is made for the structure of the device with respect to layer thickness and dielectric constants, dimensions, and wavelength and incidence angle of an impinging light beam. Operational characteristics of the device of the reference are defined by the solution to Maxwell's equation set forth in the reference, including geometry and physical constants for achieving optimal transmission or reflection of a light beam at the metal layer of the structure. However, the solutions to Maxwell's equation presented in the reference are not valid if the boundary conditions of the metal layer are changed. Accordingly, the invention describes an improved optical modulator wherein an electric, magnetic or electromagnetic field is impressed on the metallic film of the device to selectively alter, and thereby modulate, transmittance and reflectance of an impinging light beam of selected wavelength, the characteristics of which are substantially different than in the absence of an impressed field. The fields required for modulation of the light beam may be imposed by conducting a current through the metal layer or by applying microwave, millimeter wave or laser radiation into the surface of the metal layer, the controlled time variation of which results in desired modulation of the transmitted or reflected beam intensity.
It is, therefore, a principal object of the invention to provide an improved light modulator.
It is a further object to provide a device for modulating light by controlling the transmission thereof through a metallic film.
It is another object to provide a device wherein the transmission of light through a metallic film is controlled by the application of an electric, magnetic or electromagnetic field.
These and other objects of the invention will become apparent as the detailed description of representative embodiments proceeds.